The present invention relates to a technique effective for application to a wireless communication system having a phase control loop for phase modulation and an amplitude control loop for amplitude modulation, and particularly to a technique effective for application to a communication semiconductor integrated circuit device which incorporates a phase detection circuit and an amplitude detection circuit therein, and a wireless communication system such as a cellular phone with the communication semiconductor integrated circuit device built therein.
A system called “GSM (Global System for Mobile Communication)”; adopted in Europe has heretofore been known as one system of a wireless communication device (mobile communication device) such as a cellular phone. A phase modulation system called “GMSK (Gaussian Minimum Shift Keying)” wherein the phase of a carrier is shifted according to transmit data, has been used in the GSM system.
On the other hand, there has been proposed an EDGE (Enhanced Data Rates for GSM Evolution) system for a recent cellular phone. The EDGE system includes a dual mode communication function which carries out audible signal communications with GMSK modulation and performs data communications with 3π/8rotating8-PSK (Phase Shift Keying) modulation. The 8-PSK modulation is equivalent to such modulation that an amplitude shift is further added to a phase shift in carrier under the GMSK modulation. The GMSK modulation is one in which information of one bit per symbol is transmitted, whereas information of 3 bits per symbol can be transmitted in the 8-PSK modulation. Therefore, the EDGE system is capable of carrying out communications at a high transmission rate as compared with the GSM system.
As a method of realizing a modulation system for causing a phase component and an amplitude component of a transmit signal to have information, there has heretofore been known a method called “polar loop” wherein a signal to be transmitted is separated into a phase component and an amplitude component, which in turn are subjected to feedback under a phase control loop and an amplitude control loop respectively, after which they are combined by an amplifier, followed by execution of the output thereof (see, for example, “High Linearity RF Amplifier Design” by Kenington, Peter B. published by ARTECH HOUSE, INC., in 1979, pp 162).
Meanwhile, efforts are being made to take or bring as many circuits as possible in one or plural semiconductor integrated circuits in order to reduce the number of parts to thereby bring the system into less size and cost in a wireless communication system in recent years. As one of them, there is known a technique for incorporating a transmitting oscillator into a communication semiconductor integrated circuit device (hereinafter called “high-frequency IC”) having a modem function. As to a high-frequency IC constituting a GSM type communication system, one in which a transmitting oscillator is on-chipped, has been developed and proposed by the present applicant (see Patent Document 1).
Patent Document 1
Japanese Unexamined Patent Publication No. 2003-048525 corresponds to U.S. Ser. No. 10/253,922 filed on Sep. 9, 2002.